1) Field of the Invention
The subject invention generally relates to a method of transferring energy in an optical fiber amplifier or laser structure. More specifically, the subject invention relates to a method of transferring energy from a cladding element to a core element by migration of the energy within an energy migration component found in the cladding and core elements to an active gain component in the core element. In some embodiments the core element includes a sensitizer in addition to the energy migration component and the active gain component. In other embodiments, the energy migration component located in the core elements functions as the active gain component.
2) Description of Related Art
Methods of transferring energy in optical fiber amplifiers and laser structures are known in the art. To transfer energy, many of these methods rely on pumping the cladding elements of the optical fiber amplifier or laser structures. As is known in the art an optical fiber laser is basically an amplifier with feedback. Cladding-pumped optical fiber laser structures are utilized throughout the medical and telecommunication industries. More specifically, cladding-pumped optical fiber laser structures and systems have advanced the state-of-the-art in these industries by permitting pumping of single-mode core elements with multi-mode high power pumping sources. As a result, optical fiber laser structures can be developed with power densities that are only limited by material considerations and the ability to introduce energy, through the pumping sources, into the optical fiber laser structure.
One example of a method that relies on pumping the cladding element of the optical fiber laser structure is disclosed in U.S. Pat. No. 5,291,501. This method, and other conventional methods of pumping the cladding element, are deficient for various reasons. The method disclosed in the '501 patent is deficient because, to effectively transfer energy from the pumping source to the core element, this method requires pumping of an active gain component in the cladding element, specifically Nd, such that the active gain component in the cladding element actually lases. If lasing is not achieved in the cladding element, then the energy is not effectively transferred from the pumping source to the core element, i.e., the core element does not lase. Reliance on lasing to transfer energy from the cladding element to the core element creates a range of difficulties in utilizing this technology.
The method of pumping the cladding element of the optical fiber laser structure disclosed in U.S. Pat. No. 5,530,710 is deficient for similar reasons. Like the '501 patent, the method disclosed in the '710 patent utilizes an intermediate four-level active gain component to convert the energy from the pumping source into energy that is suitable for pumping a three-level active gain component. This method is, therefore, unable to directly pump a three-level active gain component without relying on first pumping of the intermediate four level active gain component.
Due to the deficiencies in the prior art methods for transferring energy from a cladding element to a core element in cladding-pumped optical fiber structures, including those identified above, it is desirable to implement a method of transferring energy in an optical fiber amplifier or laser structure that uses migration of the energy from an energy migration component in a cladding element to an active gain component in a core element such that the active gain component lases or provides amplification gain.